'Ramones probably sell more T-shirts now than they did records in their heyday' ... Hayley Williams of Paramore sports a Ramones shirt. Photograph: Joey Foley/Getty

My first was REM. It was white, loose, and had a chequerboard on the front. I bought it, secretly, from the back pages of NME; I ran for the postman every morning, before my mother did, to check if it had arrived. The day it came, I ran upstairs, locked the door and put it on. Fifteen years old, there I was in my first band T-shirt – and just like that, I felt part of something.

The band T-shirt is one of music's most potent totems. Pull one over your head and it points out an allegiance, however confident or timid the wearer. Six months ago, Ian Wade and I started a blog, My Band T-Shirt, to tell their stories: me beginning with an Orbital top given to me by a boyfriend, Ian following with a tale of living in a Blur top for a year. Inviting others to post stories, we were staggered by the emotions bundled up in them: people gave birth, lived and died in the shadow of their screenprint; life's rich tapestry revealed itself through these scraps of cotton.

Band T-shirts first appeared 50 or so years ago. Names of groups started popping up on children's clothes in the mid-60s, an extension of the trend for comic book T-shirts in Mad magazine. The Beatles and the Dave Clark Five were early adopters, two bands that understood merchandising. Then came the hippy phenomenon of tie-dye with a logo slapped on top. Johan Kugelberg, author of Vintage Rock T-Shirts, doesn't put their success down to the power of music, however. "What broke band T-shirts was mass distribution, just like everything else."

The idea of branding yourself with a musician's name wasn't new, according to Kugelberg. "Bobby-soxers [in the 40s] began the trend of writing the name of their favourite singer across the back of their jackets – a flourish of Frank, or a swirl of Sinatra. Band T-shirts were a later extension of that." By broadcasting love for an artist on their chest, Kugelberg says, a person could suggest a mystical connection between themselves and a superstar.

The band T-shirt reveals contradictory impulses in its owner, especially when that owner is a teenager. It marks a desire to be seen differently, but also to fit in; it signifies a split from your parents, but also a wish to be part of an alternative group of peers, even if you haven't met them yet. On our blog, Stevie Chick claims, tongue in cheek, that his T-shirts reveal "exquisite taste and enviable cultural nous"; Sarah Drinkwater confesses to using her Blur Mile End Stadium T-shirt to pretend she had attended the 1995 gig, when in fact she cried off at the last minute, afraid of her father's reaction if he found out she'd been; Andrew Denney was too scared to wear his Pet Shop Boys T-shirt, fearing it might mark him out in darkest Cheshire.

Kugelberg thinks T-shirts are status symbols. "They're middle-class luxury items, no doubt. It's luxury consumption. It's what brand you slap across your chest." However, this doesn't explain the hymns to self-made T-shirts that have been sent to our site – including a David Bowie logo reappropriated from a too-tight pink top, or the disastrous Sweet T-shirt made by Mark Wood ("The end result was bits of melting the Sweet faces all over the place and an iron that had to be thrown away"). The need to associate with a star, ironing disasters and all, is about much more than money.

More than anything, band T-shirts are about communicating hidden messages. In hindsight, I know how much meaning I inscribed to my Oasis Shakermaker T-shirt, worn to my first day at college, bought with paper-round money. It said: be gone, school; be gone, uniform; be gone financial dependence; hello all you new people who might understand me. Dick Hebdige's 1979 sociological classic Subculture: The Meaning of Style framed these feelings in academic lingo: "It is through the distinctive rituals of consumption, through style, that subculture at once reveals its 'secret' identity and communicates its forbidden meanings."

That explains why band T-shirts are often embraced by alternative genres, and why after tie-dye, the rock T-shirt market was dominated by the black cotton of heavy metal. The grunge boom did similar business, but irony also came into play, with naff logos of soft rock bands such as Boston worn as signs of self-awareness. Later, this trend was adopted by the mainstream, and soon band T-shirts trickled into high street fashion. In the last decade, there were MC5 T-shirts in Topman, Velvet Underground tops in Urban Outfitters and AC/DC baby outfits. David Beckham, at the peak of his turn-of-the-century fame, was pictured wearing a T-shirt bearing the Crass logo picked out in diamanté studs. Here, T-shirts were simply the vehicles for the communication of a vague kind of "cool", unrelated to the messages the original wearers had wanted to convey.

Sometimes, T-shirts would become better known than the band. Ramones probably sell a great many more T-shirts now than they did records in their heyday. Twenty years ago, it was James – thanks to a T-shirt with a flower on the front, and the band name spelled, letter by letter, on the body, sleeve and back.

James's singer, Tim Booth, knew why the shirts appealed. "They were cool at the start because we weren't mainstream. We'd been going for seven years; we'd only been played on John Peel." But then came Sit Down, which reached No 2 in 1991, and Booth thinks the T-shirt's sudden ubiquity showed how the message of that song had been recognised. At their gigs, Booth would stare out at seas of the shirts. "It was phenomenal. But [Sit Down] was all about people who felt like outsiders coming together – and that was what the T-shirt suggested, rather than what it said." The band still revive an old T-shirt for every tour, but Booth is keen to distance the band from a logo that overwhelmed them – so much so that when NME said, incorrectly, that James had made millions from T-shirts, the band had their tax accounts frozen for three years. "The act of buying the T-shirt wasn't an image thing," Booth says. "They were worn by all sorts of normal people who had reacted to a cue in our music, a lyric, a song; that's what they were about."

But why do we still cling on to band T-shirts as adults? It's partly nostalgia, Kugelberg says, but it goes deeper than that. "It's like Chumbawamba said: we sing songs that remind us of the good times, we sing songs that remind us of the bad times. It's about using moments of our frivolous youth as comforters." A T-shirt can help us acknowledge the changes we've gone through in our lives. "When we're approaching middle age, we want to show why we were part of something meaningful. Especially now, when everything is so accessible. Consumption now moves at hyperspeed, and we [as adults] are incapable of tracking the passions of youth – so we acknowledge ours in this way."

Perhaps it is telling that the most touching posts on our site have involved T-shirts that have been thrown away. John Earls got rid of his when he moved in with his girlfriend. The boyfriend who gave me my Orbital T-shirt, which I still wear to clean the house, regretted a T-shirt cull of his own: "As a public information warning, I urge you: don't throw them out."

After six months of our site, I thought I knew what band T-shirts are: part of our dust, part of our past to move on from. But then I read Jeanette Leech on the gift of a Madonna T-shirt after the death of a parent: "It was one of the earliest reminders I had that yes, there was still a me in that miserable little bundle of nerves." Or Brad Sanders on his Blind Guardian top: "I'm still fundamentally that awkward 13-year-old kid in a Nightfall in Middle-Earth T-shirt." Band T-shirts may stain, tear and age, but forget them completely, and we forget who we are, too.

To contribute your own T-shirt, go to mybandtshirt.tumblr.com. Johan Kugelberg's Vintage Rock T-Shirts is published by Universe. James's box set The Gathering Sound is released Monday on Mercury.